A reagent injection system for a catalytic emissions reduction assembly of a combustion turbine that includes an exhaust duct and at least one injector. The exhaust duct includes a first section including an entrance end and an exit end, wherein the entrance end is configured to be fluidly coupled to the combustion turbine to receive exhaust gases therefrom. The exhaust duct also includes and a second section having an entrance end that is fluidly coupled to the exit end of the first section. The at least one injector is operatively coupled to one of the first and second sections, and each injector is configured to inject a reagent into the exhaust gases flowing through the exhaust duct.